Rubber stamp inking pad



4 Sept 7, 1954 H. E. NlcHoLs HAL 2,688,307

RUBBER STAMP INKING PAD Filed Feb. 17, 1949 3 snee-ts-sheethl attorneys Sept 7, 1954 H. E. NICHOLS ET AL 2,688,307

RUBBER STAMP INKING PAD Filed Feb. 17, 1949 3 Sheets-Sheet 2 Snoentors .ePt- 7, 1954 H. E. NICHOLS rs1-AL 2,688,307

RUBBER STAMP INKING PAD S'ld Feb. 17, 1949 3 Sheets-Sheet 5 u u MT@ n (Ittomegs Patented Sept. 7, 1954 2,688,307 RUBBER STAMP INKING PAD Horace E, Nichols and George Howlett Davis, Detroit, Mich.; said Davisassgnor to said Nichols Application February 17, 1949, Serial No.

01. 1ra-e264) 6 claims. 1

This invention relates to inlring devices and, in particular, to ink transfer devices such as stamp pads and the like.

One object of this invention is to provide an ink transfer device, wherein the inl: holding and transferring portion is composed substantially entirely of finely divided particles, such as pow.- dered metal, the ink feeding up through the device by means of capillary attraction.

Another object to provide Aan inl; 'transfer device, in-cluding an ink pad made py powder metallurgy, wherein tiny particles of metal are pressed together to form a porous plate.

Another object is to provide an inl; transfer device, as set forth in the preceding objects, wherein an ink reservoir is provided beneath the pad by forming recesses or passageways either in the pad or in the portion of the base adjacent the pad.

Another object is to provide an transfer device, as set forth in the preceding objects, wherein the base is provided with a slidingcover which may be mounted in one position to expose the ink pad and in another position to conceal tand protect it.

Another object is to provide an transfer device, as set forth in the preceding objects, wherein the ink deposits only y a .thin Kfilm on the top of the pad and .does -not spreadup the sides of the rubber Stamp, to be used for many stampings before any in vthe density of the stamp.

Another object is Ito provide an inl; transfer device, as set forth `in .the preceding objects, wherein the all-metal construction of the pad appreciable change occurs impression made rhy the latter is pressed down upon it.

Another object is Ato provide an inl; transfer device, as set forth in the preceding objects. wherein the base beneath-the ink pad is provided on its lower surface with minute capillary ink grooves radiating outward to the margin from a :filling hole inthe center, these grooves vbeing Another object is `to provide an ink transfer device, as .set forth in the object immediately preceding, wherein the marginal breather pasthereby enabling the pad thousand impressions vor 2 Sager/ars are pmvided i@ equalize me rtessure 011 the ink resulting from temperature phen es, in i e room where .it is, used, thereby rr-sie s flooding after the device has stood overnight in a .con 'room which is then ,hatd to e were tem? nera-.tureln the drawings:

Figure lis a ier-Plan View 0f an ink transfer device according to ,one form 0f the ieveniisln with the Pad and base Partly .breken @Wer t9 Shaw the underlying structure;

Figur@ 2 is e vertical .Cross-gestion @1911 the line '2*3 Figure l;

Figure 3 is a vertical .leneiiufiinal ,section ,i1-,lees the line V3---3 in Figure 2;

Figure 4 is a perspective v iew of the ink transf fer device Show-11 in Figures 1 and 2, with the cover thereof slid back partvvay from y.its protect.- ing position;

VFigure 5 ,is a cross-section through la `vinedined ink transfer device, lgenerally similar to Figure x2, but having inl; reservoir recesses Ein the 4bottor'n of the pad;

Figure 6 is a cross-section through a further modified ink transfer device, Ywi'ie'rein the pad is provided ,with longitudinal inl:V passageway/lis" ink pad successivelybroken underlying construction;

Figure 8 is a side elevation, partly in k.vertical section, along the line V8-B in Figure 7; u Figure 9 is a `,vertical ycross-section taken along the line 9-9 in Figure 7 4at right angles to the vertical ksection shown in lFigure l8.;KV Figure l0 is an yenlarged .fragmentary vertical section taken along the line .ill in lFigure l2; Figure -11 -is a fragmentary vertical section along the line H H in Figure 7.;

Figure 12 is an enlarged fragmentary .top .plan View of one quarter of `the ink reservoir lying beneath the metallic ink pad; Figure 13 is a .vertical section along ,the line [35H3 in Figure l1 2,,takenthrough oney of the division ridges between the ink grooves;

through thefedgeof the inl; reservoir, .taken along the line l-i-l4 in Figure 12; `and Figure 15 is an enlarged tfragmentary vertical section similar to Figure l10,but showing a modi,- fication wherein the grooves are placed in the transfer pad rather than inthe base.

Referring tothe drawings in detail, ,Figures 1, 2 and 4 showanfinkitransfer device, generally designated H), according to one form of the infvention, as consisting generally of a base II, an ink transfer pad I2 seated therein and a sliding cover I3 slidably mounted on the base II. base I I is of any suitable shape, the outline shown being rectangular and provided with longitudinal rectangular grooves III which serve to receive tongues or fianges I5 which extend inward from the opposite lateral edges I6 of the cover I3. The coverl I3 has a top portion II bridging the edge portions I6 and serving to cover and protect the pad I2. At least one end of the cover I3 is open so as to permit the base and its pad I2 to be slid into the interior of the cover I3. The base II and cover I3 are conveniently made of molded plastic material.

The base I I is provided with a recess I8 (Figure 2) preferably having a flat bottom I9 and slightly inclined edges 20. By this means the pad I2 can be forced into the recess I8 and anchored therein by the resilience of the pad I2 and base II. The base II (Figure 2) is provided with spaced parallel grooves 2| which serve asv reservoirs to hold the ink with which the device is supplied. In order to hold the cover I3 yieldably against the base I I, a leaf spring 22 (Figures 1 and 3) is mounted in one of the grooves I4 and yieldingly and frictionally engages the adjacent rib or flange I5. In order to fill the reservoir groove or recesses 2| with ink, the grooves II are interconnected by a transverse groove or header 23. Opening into the header groove 23 is a threaded hole 24 closed by a screw plug 25.

The pad I2 is formed preferably of metal particles joined together by the conventional process of powder metallurgy, the process itself being well-known in the metallurgical art and, therefore, requiring no detailed description. According to this process, the particles of metal, preferably tiny spheres, are forced together in a die by means of a press, and are then sintered to unite them. Thus, the metal spheres are separated from one another by interstices of microscopic proportions, these interstices forming minute passageways through which the ink will climb by means of capillarity. One type of pad which has been found to work satisfactorily is formed of bronze particles united by being pressed together and sintered. The pad I2 has a substantially smooth flat extended working surface on its upper side as is self-evident from the drawings.

In the operation of the invention, the screw plug 25 is removed and a suitable ink is introduced therethrough, preferably by means of a pressure gun or syringe, so as to fill the passageways or grooves 2| with ink distributed thereto from the transverse header groove 23. When the ink emerges from the pores in the top of the pad I2 and the latter is suitably covered with a lm of ink, the filling is terminated. The screw plug 25 is then re-inserted in the threaded hole 24 and the pad is ready for use.

The ink used with the present invention must not leave a residue which will clog the pores. It should also preferably be of a type which has a relatively low viscosity and also easily vvets the metal particles of which the pad is constructed. Certain inks which are available on the market for use with ball-pointed fountain pens have been found satisfactory as they are suiiiciently thin to flow readily by capillary attraction through the pores of the pad, they wet the metal particles and they do not clog the pores of the pad.

In the use of the invention, the cover I3 is slid off the base II in the manner indicated in Figure 4, and slid back onto the base in an inverted position as shown in Figure 2. This prevents loss of the cover I3, and also adds to the weight of the device so that it does not slide around too easily on a desk or table. The rubber stamp which is to be inked is pressed down upon the top surface of the pad I2 in the usual way and a thin coating of ink is transferred from the top of the pad I2 to the bottom surface of the rubber stamp. When the term rubber is employed herein, it is also understood that synthetic rubber or any elastic deformable material of rubber-like properties may also be used and is intended to be included.

From experience with the present invention, it has been found that many thousand impressions may be made with an ordinary rubber stamp with very little change in the density of the inscription made on the paper upon which the stamp is subsequently impressed. Many thousand more impressions may be made before the device requires recharging. The present ink transfer device operates as long as the ink is in contact with the pad and this occurs as long as there is any ink in the reservoir grooves 2|. As rapidly as ink is removed from the top surface of the pad I2 by the rubber stamps, more ink flows to the top surface through the pores of the pad by means of the force of capillarity. Even though the ink is temporarily depleted from the center portion of the pad I2, other ink flows through the pores and automatically redistributes itself over the pad.

rIhe modification shown in Figure 5 is generally similar to the form of the invention shown in Figures l to 4 inclusive, and similar parts are similarly designated. The pad I2 of Figure 5, however, is provided with grooves 26 in the bottom of the pad itself in place of the grooves 2| in the bottom of the recess I8. The grooves 2G, like the grooves 2| will, of course, interconnect by a cross groove (not shown), similar to the transverse groove or header 23.

The operation of the modification is also substantially the same as that of the form of the invention shown in Figures l to 4 inclusive, and hence requires no repetition.

The modification shown in Figure 6 is also generally similar to the form of the invention shown in Figures 1 to 4 inclusive, and similar parts are also similarly designated. In this modification, the grooves 2| are omitted from the base I I, and the pad itself is provided with longitudinal passageways 21 which serve as reservoirs for the ink. These are also suitably interconnected by a transverse passageway (not shown) similar to the header groove 23 and leading to a filling aperture similar to the filling aperture 24 of Figure 1. The operation of this modification is likewise similar to that of the form of the invention shown in Figures 1 to 4 inclusive and hence requires no repetition.

While the present invention has been described particularly as regards its application for use with rubber stamp pads, it will also be evident that it may be used for other purposes where ink is to be transferred. The pad, for example, may be used for taking fingerprints, merely by placing the fingers upon the pad to coat them with a thin The fingers may then be removed from the pad and pressed down upon the paper record sheet or card in the usual manner. The present invention provides a thinner film than the ordinary pad of textile material, hence requires less ink and, accordingly enables the impressions made by the rubber stamp or fingers to penetrate more rapidly than with the conventional pads.

The ink transfer device of the present invention is a virtually indestructible pad which is substantially unaffected by atmospheric conditions, which is easily cleaned, which does not easily absorb foreign materials and which can be easily wiped off. Since the pad itself is of metal, it has a very long life and, hence, requires replacement very infrequently in comparison with the ordinary inking pads of textile material.

The modiiied ink transfer device, generally designated 30, shown in Figures '7 to 14 inclusive, consists generally of an ink reservoir base 3| upon which is superimposed 1a porous metallic ink transfer pad 32 around which extends a border frame 33, the whole being closed by a slideable cover plate 34. The ink transfer pad 32 is of similar construction to the ink pad l2 in that it is likewise formed of minute metal particles joined together by the conventional process of powder metallurgy, as described above in connection with the forms of the invention shown in Figures 1 to 6 inclusive. The pad 32 has a substantially smooth flat extended working surface on its upper side, as is self-evident from the drawings. The ink transfer device has the improved advantages of causing the ink to flow more evenly throughout the ink transfer pad 32 as well as to prevent flooding of the pad by the ink as the result of changes of temperature.

rihe base 3| is preferably of molded synthetic plastic or other suitable material and consists of a central plate-like portion 35 having inner and outer circular flanges 36 and 31 (Figure 9) likewise having a central tapered opening 38 in a boss 39 and closed by a plug 40. This is for the purpose of filling the device with ink, as described below. The plate-like portion 35 is preferably of approximately rectangular outline and is surrounded by a depressed portion 4| forming an ink channel or well 42 extending entirely around the plate-like portion 35. The depressed portion 4| is surrounded on its outer edge by a downwardly-extending flange 43 which, with the flanges 36 and 31 provides strengthening of the base 3|.

In order to provide additional strengthening, diagonal ribs 44 (Figures 7 and 11) are also molded into the base 3|, radiating outward from the central circular flange 36 through the outer circular flange 31 to the peripheral flange 43. The outer flange 43 continues upward in a slightly inset vertical ange `45 providing an annular shoulder 46 which is approximately the thickness of the border frame 33 so as to be substantially flush therewith as described below.

The marginal flange 43 is provided with `spaced rounded edge portions 41 (Figure 11) leading to internal bosses 49 thereon. These are engaged by corresponding projections 61 on the cover 34, as explained below, when the :latter is slid beneath the base 3| in a manner analogous to the position of 'the cover shown in Figure 2. Certain of the diagonal ribs 44 are provided ywith grooves 4B (Figures 7 and 1l) for the passage of the projections 61.

The upper surface of the plate-like portion 35 isprovided at its central area with a multiplicity of frusto-conical protuberances 50 occupying a central recess or receptacle 5| of rectangular outline to which ink is supplied lthrough the central filling opening 33. The protuberances 50 are very .close together `so that their interstices form crevices '52 into which the ink is drawn and tiges by capillary action. Radiating outward from the central recess 5| are minute capillary ink grooves 53 which are of approximately V- shaped cross-section (Figure 10) and which are also inclined downward at their bottoms from a comparatively shallow depth at their inner ends (Figure 13) to a considerably greater depth at their outer ends. The capillary ink ,grooves 53 are separated from `one another by flat-topped ridges 54, the sloping sidewalls 55 of which form the side walls of the grooves 53. The inclined side walls 53 on the opposite sides of each ridge 54 meet at their outer ends in an approximately conical end surface 56 (Figure 12) and these, in turn, extend downward into the ink channel or well 42 in semi-cylindrical portions 51. Thus, the grooves 53 not only deepen from` their inner ends to their outer ends, but they also widen in the same direction, being flared slightly as they proceed outward. The inner ends of the ridges 54 are similarly rounded as at 58 with frusto-conical ends having smaller radii of curvature because of the narrower widths of the grooves 53 at their inner ends.

The border frame 33 has ,a downwardly-extending marginal flange 63 which is joined to a `stepped inner flange 5| (Figure 11) by a downwardly land inwardly inclined web portion 62. The flange (il and the inner edge ofthe web 6.2 are provided with a groove 63 of right-angle cross-section which ts down over the outer edge of the plate-like portion 35 and at the same time presses down on the ink transfer pad 32 and holds it in position at its margins. The frame 33 is preferably joined to the base 3| by cementing the flanges 60 and 45 together (Figure 11). In order to prevent the flooding `of the pad 32 Iby changes in atmospheric pressure beneath the cover 34 by changes in temperature, lthe border frame 33 is provided with a pair of bosses 64 having passageways 65 (Figure 9) extending from the space above the ink transfer pad .32 to the space `65a above the ink well or channel 42. In this manner, the central opening 38, the central recess 5| and the grooves 53 are always in atmospheric communication with the space above the ink transfer pad 32.

The cover 34 is provided with a plate-like top portion 66 having detent proiections 61 molded on the underside thereof, these being adapted to pass through the -grooves 41 and 43 when the cover 34 is removed from its position above the ink 'transfer pad 32 and replaced on the bottom ofthe device, as described in connection with the operation. The cover 34 is of channel-shaped cross-section having side flanges 68 (Figure 9) terminating in inwardly turned ridges 53 which are seated in the space between the shoulder 46 (Figures 9 and 11) and the lower edge of the flange 60. The latter space, in effect, provides a groove for receiving and retaining the inwardly turned ridges 69. 'The projections 61 serve as yieldable detents (Figure -8) to releasably hold the vcover 34 in its closed position by engaging the web portion v62 of the border frame 33 below its outer rim. The projections 49 on the underside yof the flange 43 similarly serve to engage the detent projections 61 when the cover 34 is placed beneath the base 3 In the operation of the `modified ink transfer device shown in Figures .'7 to .14 inclusive, the 'interstces 52 of the .central recess .5| are filled with .a vsuitable ink vby removing the plug 40, as with 4aipaper clip, and inserting the correspondingly tapered nozzle of a collapsible tube containing the ink into the central taperedopening 38 of the boss 39. The operator squeezes enough of the ink through the opening 38 into the central recess l to fill it and the capillary ink grooves 53 with ink whereupon he removes the nozzle and inserts either the old plug or, preferably, a new plug 4D. rThese plugs may consist of ordinary eyelets, hence are expendable.

The ink ows by the pressure created by collapsing the tube, through the radiating capillary V-grooves 53 to all portions beneath the porous metal ink transfer pad 32, surplus ink passing into the recess or channel 42 forming the inkwell around the periphery. As the ink becomes absorbed and used up by repeated use of the pad, the surplus. ink in the well or recess 42 will flow backward up the capillary ink grooves 53 by capillary attraction, aided by the tapered configuration of the grooves. We have found that the ink iiows naturally toward the converging or narrower part of the channel by capillary attracn tion and that even though the ink in the inkwell 42 is exhausted, any portion of the ink remaining in the grooves 53 will flow toward the smaller or inner ends of the grooves. We have found that passageways of uniform width and depth with parallel sides will not move the ink inward in this manner by capillary attraction unless aided by gravity when the device is tilted. The tapered grooves, however, will even cause the ink to flow uphill at a slight inclination. In order for the ink to iiow into the interstices between the protuberances 50 from the grooves 53, however, these interstices should be narrower than the inner ends of the tapered grooves 53 to prevent the ink from being drawn from the interstices into the grooves. This will not occur, however, if there is a continuous column of ink leading to a larger cross-section of the groove, that is, one wider than the width of the interstices. When the ink column in the grooves 53 flows nearer the center to a point where the rearward end of the column lies in a cross-section of the groove which is narrower than the width of the interstices between x the protuberances 50, the flow ceases unless the column is reconnected to a wider portion of the groove or to the inkwell 42 itself by supplying it with more ink.

These effects can be readily demonstrated by the use of a thin liquid, such as alcohol, which moves faster up the grooves 53 than does the ink or other liquids of higher viscosity.

Moreover, we have observed that the bottom surface of the metallic ink transfer pad 32 does not always fit snugly down upon the flat top ridges 54 between the capillary ink grooves 53, but frequently leaves a slight clearance. This narrow gap, however, has a benecial effect in distributing the ink, particularly when all of the ink has been exhausted from the inkwell 42 and the columns of ink in the capillary ink grooves 53 have their rearward ends disposed inward from the outer ends of the grooves 53, namely inward from the inkwell 42. Due to the tapered coniiguration of the capillary ink grooves 53, these columns of ink which are now disconnected from the inkwell channel 42 will nevertheless continue to supply ink to the outer portions of the pad since ink tends to flow backward from the rearward ends of the ink column toward the inkwell channel 42, this flow occurring in the narrow clearance space between the tops of the ridges 54 and the bottom surface of the porous metallic pad 32. A slight clearance, of the order of a 32nd of an inch, is left between the flange or skirt 6| and the outer edge of the plate-like center portion 35 of the base 3|.

Furthermore, the construction of the inkwell 42, as shown at the right-hand side of Figure 8, is such that leakage is prevented and flooding eliminated even if the device is stored or carried in an inverted position or up on edge. II" the device is inverted, the chamber of rhomboidal cross-section shown at the upper right-hand corner of Figure 8 will still hold the ink without leaking or flooding, whereas if the device is turned up on edge, the lower portion of this same chamber will hold the ink without leaking.

The modified ink transfer pad of Figures 7 to 14 inclusive will not flood overnight with ink even though the room in which it is located cools down to a low temperature in winter during the night and is heated up to a warm temperature during the day. This action alters the pressure above the ink pad 32 due to the contraction of the air as it cools down, and, without special provision to counteract it, would suck the ink up to the side of the pad 32. The little air passageways 65 (Figure 9) at the sides of the frame 33 serve to equalize the pressure between the inkwell or recess 42 and this in turn equalizes the pressure at the outer ends of all of the grooves 53 because it extends entirely around the central portion 35 of the base 3l. The oblong shape of the central portion 35 also assists in preventing ooding since the ink will reach the inkwell 42 more quickly through the shorter grooves 53 than through the longer ones, the ink in the channel 42 reaching the outer ends of the longer grooves 53 directly.

In addition to serving as air passageways to prevent ooding, the passageways S5 also serve as limiting points in preventing over-filling the device 5 with ink. When the ink, in iowing outward from the central hole 38 reaches the passageways 65 it is time for the operator to cease further filling attempts. The air chambers or spaces 65a should be larger than the passageways 55 so as to prevent the raising of ink from the ink well 42 by capillarity.

The modiiication shown in Figure 15 is similar in principle and mode of operation to that shown in Figures 7 to 14 inclusive. In the modified construction of Figure 15, however, the base 'I0 corresponding to the base 3| of Figure l0 has a smooth upper surface H whereas the ink transfer plate or pad 12 has on its bottom surface 13 a pattern of converging V-shaped capillary ink grooves 14 similar to the pattern shown in Figure 13 and similarly leading to protuberances (not shown) in the center of the bottom surface 'd3 of the plate l2. In other words, the modification of Figure l5 merely reverses the position of the capillary ink groove and protuberance pattern by placing it on the underside of the ink transfer plate or pad rather than on the upper side of the base. The mode of operation of the modification of Figure l5 is substantially the same as that of the form of the invention shown in Figures 7 to 14 inclusive and hence requires no repetition.

What I claim is:

l. A. rubber-stamp inking pad comprising a base structure having a cavity in the upper side thereof, a sintered porous powdered metal plate having a substantially smooth at extended working surface composed of a multiplicity of minute metallic particles, an ink reservoir disposed beneath the top of said plate, said ink reservoir forming a part of said cavity, and means for securing said ink reservoir to said plate in abutting relationship therewith, said particles engaging one another and having minute capillary passageways therebetween and a cover structure slidably engaging said base structure, one of said structures having a longitudinal groove in an edge thereof and the other structure having a projection slidingly engaging said groove, said cover structure having side members extending adjacent the sides of said base structure and forming a recess of sucient depth to receive said base structure either when said cover structure is positioned above or below said base structure.

2. A rubber-stamp inking pad comprising a base member having a cavity in the upper side thereof, a sintered porous powdered metal plate composed of a multiplicity of minute metallic particles secured in said cavity, said particles engaging one another and having minute capillary passageways therebetween and a cover member slidably engaging said base member, one of said members having a longitudinal groove in an edge thereof and the other member having a projection slidingly engaging said groove and a spring contact device yieldably mounted on one of said members frictionally engaging the other member.

3. A rubber-stamp inking pad comprising a base structure, a sintered porous powdered metal plate member having a substantially smooth flat extended working surface superimposed on said base structure, said base structure having an ink conduit disposed at the periphery of said plate member, an air chamber between said ink conduit and said plate member, and an air passageway extending between said air chamber and the space above said plate member, and means for securing said plate member to said base structure.

4. A rubber stamp inking pad comprising a base member, a sintered porous powdered metal plate member having a substantially smooth at extended working surface superimposed on said base member and composed of a multiplicity of minute metallic particles engaging one another and having capillary ink pasageways therebetween, one of said members having therein a central ink receptacle with a multiplicity of minute capillary ink grooves radiating outward from said receptacle, and means for securing said plate member to said base member.

5. A rubber stamp inking pad comprising a base member, a sintered porous powdered metal plate member having a substantially smooth nat extended working surface superimposed on said base member and composed of a multiplicity of minute metallic particles engaging one another and having capillary ink passageways therebetween, one of said members having therein a central ink receptacle with a multiplicity of minute capillary ink grooves radiating outward from said receptacle, said grooves being tapered inwardly toward said receptacle, and means for securing said plate member to said base member.

6. A rubber stamp inking pad comprising a base member, a sintered porous powdered metal plate member having a substantially smooth flat extended working surface superimposed on said base member and composed of a multiplicity of minute metallic particles engaging one another and having capillary ink passageways therebetween, one of said members having therein a central ink receptacle with a multiplicity of minute capillary ink grooves radiating outward from said receptacle, said grooves increasing in depth outwardly from said receptacle, and means for securing said plate member to said base member.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Re. 22,118 Lohrey June 16, 1942 1,024,193 Folger Apr. 23, 1912 1,241,322 Woody Sept. 25, 1917 1,555,180 Bronner Sept. 29, 1925 1,569,470 Falder Jan. 12, 1926 1,663,103 Thompson Mar. 20, 1928 2,051,009 Porter Aug. 11, 1936 

